reputation-core 0.1.0

use crate::error::ValidationError;
use reputation_types::AgentData;
use chrono::Utc;

/// Validates all fields of AgentData to ensure they meet required constraints.
/// 
/// This function performs comprehensive validation including:
/// - DID format validation
/// - Date validation (no future dates)
/// - Rating bounds and consistency
/// - Review count consistency
/// - MCP level validation
/// 
/// # Example
/// ```
/// use reputation_core::validation::validate_agent_data;
/// use reputation_types::AgentData;
/// use chrono::Utc;
/// 
/// let agent = AgentData {
///     did: "did:example:123".to_string(),
///     created_at: Utc::now(),
///     mcp_level: Some(2),
///     identity_verified: true,
///     security_audit_passed: false,
///     open_source: true,
///     total_interactions: 100,
///     total_reviews: 50,
///     average_rating: Some(4.2),
///     positive_reviews: 40,
///     negative_reviews: 10,
/// };
/// 
/// match validate_agent_data(&agent) {
///     Ok(()) => println!("Agent data is valid"),
///     Err(e) => println!("Validation failed: {}", e),
/// }
/// ```
pub fn validate_agent_data(data: &AgentData) -> Result<(), ValidationError> {
    validate_did(&data.did)?;
    validate_dates(data)?;
    validate_ratings(data)?;
    validate_review_counts(data)?;
    validate_mcp_level(data.mcp_level)?;
    validate_interactions(data)?;
    Ok(())
}

/// Validates DID format according to W3C DID specification.
/// 
/// DIDs must start with "did:" followed by a method name and method-specific identifier.
/// Also performs security validation to prevent malicious inputs.
/// 
/// # Examples
/// - Valid: "did:example:123", "did:web:example.com", "did:key:z6MkpTHR8VNsBxYAAWHut2Geadd9jSwuBV8xRoAnwWsdvktH"
/// - Invalid: "example:123", "DID:example:123", "", "did:", "did::"
fn validate_did(did: &str) -> Result<(), ValidationError> {
    if did.is_empty() {
        return Err(ValidationError::InvalidDid("DID cannot be empty".to_string()));
    }
    
    // Security: Check for path traversal attempts
    if did.contains("..") || did.contains("//") {
        return Err(ValidationError::InvalidDid(
            "DID contains invalid path sequences".to_string()
        ));
    }
    
    // Security: Check for script injection attempts
    if did.contains('<') || did.contains('>') || did.contains("javascript:") {
        return Err(ValidationError::InvalidDid(
            "DID contains invalid characters".to_string()
        ));
    }
    
    // Security: Check for SQL injection patterns
    if did.contains('\'') || did.contains('"') || did.contains(';') || did.contains("--") {
        return Err(ValidationError::InvalidDid(
            "DID contains invalid characters".to_string()
        ));
    }
    
    // Security: Check for null bytes and control characters
    if did.contains('\0') || did.contains('\n') || did.contains('\r') || did.contains('\t') {
        return Err(ValidationError::InvalidDid(
            "DID contains invalid control characters".to_string()
        ));
    }
    
    // Security: Reasonable length limit
    if did.len() > 1000 {
        return Err(ValidationError::InvalidDid(
            "DID exceeds maximum length".to_string()
        ));
    }
    
    if !did.starts_with("did:") {
        return Err(ValidationError::InvalidDid(
            "DID must start with 'did:' prefix".to_string()
        ));
    }
    
    // Check for basic DID structure: did:method:method-specific-id
    let parts: Vec<&str> = did.split(':').collect();
    if parts.len() < 3 {
        return Err(ValidationError::InvalidDid(
            "DID must have format 'did:method:id'".to_string()
        ));
    }
    
    // Validate method name (second part)
    let method = parts[1];
    if method.is_empty() {
        return Err(ValidationError::InvalidDid(
            "DID method name cannot be empty".to_string()
        ));
    }
    
    // Validate method-specific identifier (third part and beyond)
    let identifier = parts[2..].join(":");
    if identifier.is_empty() {
        return Err(ValidationError::InvalidDid(
            "DID method-specific identifier cannot be empty".to_string()
        ));
    }
    
    Ok(())
}

/// Validates date fields to ensure they are not in the future.
fn validate_dates(data: &AgentData) -> Result<(), ValidationError> {
    let now = Utc::now();
    
    if data.created_at > now {
        return Err(ValidationError::FutureDate(format!(
            "created_at ({}) cannot be in the future", 
            data.created_at.to_rfc3339()
        )));
    }
    
    Ok(())
}

/// Validates rating values and consistency.
/// 
/// Ensures:
/// - Average rating is between 1.0 and 5.0 (inclusive) when reviews exist
/// - Average rating is None when there are no reviews
/// - Rating values are not NaN or infinite
fn validate_ratings(data: &AgentData) -> Result<(), ValidationError> {
    match (data.average_rating, data.total_reviews) {
        (Some(rating), reviews) if reviews > 0 => {
            // Check for NaN or infinite values
            if rating.is_nan() || rating.is_infinite() {
                return Err(ValidationError::InvalidRating(rating));
            }
            
            // Check rating bounds
            if rating < 1.0 || rating > 5.0 {
                return Err(ValidationError::InvalidRating(rating));
            }
        },
        (Some(rating), 0) => {
            // If there are no reviews, there shouldn't be an average rating
            return Err(ValidationError::InvalidField {
                field: "average_rating".to_string(),
                value: format!("{} (but total_reviews is 0)", rating),
            });
        },
        (None, reviews) if reviews > 0 => {
            // If there are reviews, there should be an average rating
            return Err(ValidationError::InvalidField {
                field: "average_rating".to_string(),
                value: format!("None (but total_reviews is {})", reviews),
            });
        },
        _ => {}, // None rating with 0 reviews is valid
    }
    
    Ok(())
}

/// Validates review count consistency.
/// 
/// Ensures positive_reviews + negative_reviews = total_reviews
fn validate_review_counts(data: &AgentData) -> Result<(), ValidationError> {
    // Use checked_add to prevent overflow
    let calculated_total = match data.positive_reviews.checked_add(data.negative_reviews) {
        Some(total) => total,
        None => {
            // Overflow occurred - this is definitely inconsistent
            return Err(ValidationError::InconsistentReviews);
        }
    };
    
    if calculated_total != data.total_reviews {
        return Err(ValidationError::InconsistentReviews);
    }
    
    Ok(())
}

/// Validates MCP level is within allowed range (0-3).
fn validate_mcp_level(level: Option<u8>) -> Result<(), ValidationError> {
    if let Some(mcp) = level {
        if mcp > 3 {
            return Err(ValidationError::InvalidMcpLevel(mcp));
        }
    }
    
    Ok(())
}

/// Validates interaction counts and their relationships.
/// 
/// Ensures:
/// - Total reviews doesn't exceed total interactions
/// - Values are logically consistent
fn validate_interactions(data: &AgentData) -> Result<(), ValidationError> {
    // Reviews can't exceed total interactions
    if data.total_reviews > data.total_interactions {
        return Err(ValidationError::InvalidField {
            field: "total_reviews".to_string(),
            value: format!(
                "{} (exceeds total_interactions: {})", 
                data.total_reviews, 
                data.total_interactions
            ),
        });
    }
    
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::Duration;

    fn create_valid_agent() -> AgentData {
        AgentData {
            did: "did:example:123".to_string(),
            created_at: Utc::now() - Duration::days(1),
            mcp_level: None,
            identity_verified: false,
            security_audit_passed: false,
            open_source: false,
            total_interactions: 0,
            total_reviews: 0,
            average_rating: None,
            positive_reviews: 0,
            negative_reviews: 0,
        }
    }

    #[test]
    fn test_valid_agent_data() {
        let agent = create_valid_agent();
        assert!(validate_agent_data(&agent).is_ok());
    }

    #[test]
    fn test_valid_did_formats() {
        let valid_dids = vec![
            "did:example:123",
            "did:web:example.com",
            "did:key:z6MkpTHR8VNsBxYAAWHut2Geadd9jSwuBV8xRoAnwWsdvktH",
            "did:ethr:0x1234567890123456789012345678901234567890",
            "did:ion:EiDyOQbbZAa3aiRzeCkV7LOx3SERjjH93EXoIM3UoN4oWg",
            "did:test:foo:bar:baz", // Multiple colons in identifier
        ];

        for did in valid_dids {
            assert!(validate_did(did).is_ok(), "DID '{}' should be valid", did);
        }
    }

    #[test]
    fn test_invalid_did_formats() {
        let test_cases = vec![
            ("", "DID cannot be empty"),
            ("example:123", "DID must start with 'did:'"),
            ("DID:example:123", "DID must start with 'did:'"),
            ("did:", "DID must have format"),
            ("did::", "DID method name cannot be empty"),
            ("did:example", "DID must have format"),
            ("did:example:", "DID method-specific identifier cannot be empty"),
            ("did::123", "DID method name cannot be empty"),
        ];

        for (did, expected_msg) in test_cases {
            let result = validate_did(did);
            assert!(result.is_err(), "DID '{}' should be invalid", did);
            let err_msg = result.unwrap_err().to_string();
            assert!(err_msg.contains(expected_msg), 
                "Error message '{}' should contain '{}'", err_msg, expected_msg);
        }
    }

    #[test]
    fn test_very_long_did() {
        // Test that DIDs up to the limit are accepted
        let long_identifier = "x".repeat(987); // "did:example:" is 12 chars, so 987 + 12 = 999 < 1000
        let long_did = format!("did:example:{}", long_identifier);
        assert!(validate_did(&long_did).is_ok());
        
        // Test that DIDs over the limit are rejected
        let too_long_identifier = "x".repeat(989); // 989 + 12 = 1001 > 1000
        let too_long_did = format!("did:example:{}", too_long_identifier);
        assert!(matches!(
            validate_did(&too_long_did),
            Err(ValidationError::InvalidDid(msg)) if msg.contains("exceeds maximum length")
        ));
    }

    #[test]
    fn test_future_date_validation() {
        let mut agent = create_valid_agent();
        agent.created_at = Utc::now() + Duration::days(1);
        
        let result = validate_agent_data(&agent);
        assert!(matches!(result, Err(ValidationError::FutureDate(_))));
    }

    #[test]
    fn test_date_edge_cases() {
        let mut agent = create_valid_agent();
        
        // Exactly now should be valid
        agent.created_at = Utc::now();
        assert!(validate_dates(&agent).is_ok());
        
        // Far past should be valid
        agent.created_at = Utc::now() - Duration::days(3650); // 10 years ago
        assert!(validate_dates(&agent).is_ok());
    }

    #[test]
    fn test_rating_validation() {
        let mut agent = create_valid_agent();
        
        // Valid ratings with reviews
        agent.total_reviews = 10;
        agent.positive_reviews = 8;
        agent.negative_reviews = 2;
        agent.total_interactions = 20;
        
        let valid_ratings = vec![1.0, 2.5, 3.0, 4.5, 5.0];
        for rating in valid_ratings {
            agent.average_rating = Some(rating);
            assert!(validate_ratings(&agent).is_ok(), 
                "Rating {} should be valid", rating);
        }
        
        // Invalid ratings
        let invalid_ratings = vec![0.0, 0.9, 5.1, 6.0, -1.0, 10.0];
        for rating in invalid_ratings {
            agent.average_rating = Some(rating);
            let result = validate_ratings(&agent);
            assert!(matches!(result, Err(ValidationError::InvalidRating(_))),
                "Rating {} should be invalid", rating);
        }
    }

    #[test]
    fn test_rating_special_values() {
        let mut agent = create_valid_agent();
        agent.total_reviews = 10;
        agent.positive_reviews = 10;
        agent.total_interactions = 10;
        
        // NaN
        agent.average_rating = Some(f64::NAN);
        let result = validate_ratings(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidRating(_))));
        
        // Positive infinity
        agent.average_rating = Some(f64::INFINITY);
        let result = validate_ratings(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidRating(_))));
        
        // Negative infinity
        agent.average_rating = Some(f64::NEG_INFINITY);
        let result = validate_ratings(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidRating(_))));
    }

    #[test]
    fn test_rating_consistency() {
        let mut agent = create_valid_agent();
        
        // No reviews but has rating
        agent.total_reviews = 0;
        agent.average_rating = Some(4.5);
        let result = validate_ratings(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidField { field, .. }) if field == "average_rating"));
        
        // Has reviews but no rating
        agent.total_reviews = 10;
        agent.positive_reviews = 6;
        agent.negative_reviews = 4;
        agent.total_interactions = 10;
        agent.average_rating = None;
        let result = validate_ratings(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidField { field, .. }) if field == "average_rating"));
    }

    #[test]
    fn test_review_count_validation() {
        let mut agent = create_valid_agent();
        
        // Valid: positive + negative = total
        agent.positive_reviews = 10;
        agent.negative_reviews = 5;
        agent.total_reviews = 15;
        agent.total_interactions = 20;
        assert!(validate_review_counts(&agent).is_ok());
        
        // Invalid: doesn't add up
        agent.total_reviews = 20;
        let result = validate_review_counts(&agent);
        assert!(matches!(result, Err(ValidationError::InconsistentReviews)));
    }

    #[test]
    fn test_review_count_edge_cases() {
        let mut agent = create_valid_agent();
        
        // All zeros
        assert!(validate_review_counts(&agent).is_ok());
        
        // Only positive reviews
        agent.positive_reviews = 100;
        agent.total_reviews = 100;
        agent.total_interactions = 100;
        assert!(validate_review_counts(&agent).is_ok());
        
        // Only negative reviews
        agent.positive_reviews = 0;
        agent.negative_reviews = 50;
        agent.total_reviews = 50;
        assert!(validate_review_counts(&agent).is_ok());
        
        // Large numbers
        agent.positive_reviews = 1_000_000;
        agent.negative_reviews = 500_000;
        agent.total_reviews = 1_500_000;
        agent.total_interactions = 2_000_000;
        assert!(validate_review_counts(&agent).is_ok());
    }

    #[test]
    fn test_mcp_level_validation() {
        // Valid levels
        for level in 0..=3 {
            assert!(validate_mcp_level(Some(level)).is_ok(), 
                "MCP level {} should be valid", level);
        }
        
        // None is valid
        assert!(validate_mcp_level(None).is_ok());
        
        // Invalid levels
        for level in 4..=10 {
            let result = validate_mcp_level(Some(level));
            assert!(matches!(result, Err(ValidationError::InvalidMcpLevel(_))),
                "MCP level {} should be invalid", level);
        }
    }

    #[test]
    fn test_interaction_validation() {
        let mut agent = create_valid_agent();
        
        // Valid: reviews <= interactions
        agent.total_reviews = 50;
        agent.positive_reviews = 30;
        agent.negative_reviews = 20;
        agent.total_interactions = 100;
        assert!(validate_interactions(&agent).is_ok());
        
        // Valid: reviews = interactions
        agent.total_interactions = 50;
        assert!(validate_interactions(&agent).is_ok());
        
        // Invalid: reviews > interactions
        agent.total_interactions = 40;
        let result = validate_interactions(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidField { field, .. }) if field == "total_reviews"));
    }

    #[test]
    fn test_complete_validation_chain() {
        let mut agent = create_valid_agent();
        
        // Set up a complex valid scenario
        agent.did = "did:web:example.com:users:alice".to_string();
        agent.created_at = Utc::now() - Duration::days(30);
        agent.mcp_level = Some(2);
        agent.identity_verified = true;
        agent.security_audit_passed = true;
        agent.open_source = true;
        agent.total_interactions = 1000;
        agent.total_reviews = 500;
        agent.average_rating = Some(4.2);
        agent.positive_reviews = 400;
        agent.negative_reviews = 100;
        
        assert!(validate_agent_data(&agent).is_ok());
    }

    #[test]
    fn test_validation_stops_on_first_error() {
        let mut agent = create_valid_agent();
        
        // Multiple errors: bad DID, future date, invalid rating
        agent.did = "not-a-did".to_string();
        agent.created_at = Utc::now() + Duration::days(1);
        agent.average_rating = Some(10.0);
        agent.total_reviews = 10;
        agent.positive_reviews = 5;
        agent.negative_reviews = 5;
        
        let result = validate_agent_data(&agent);
        // Should get DID error first
        assert!(matches!(result, Err(ValidationError::InvalidDid(_))));
    }

    #[test]
    fn test_unicode_did_validation() {
        let unicode_dids = vec![
            "did:测试:123",
            "did:тест:456",
            "did:テスト:789",
            "did:example:用户:alice",
        ];
        
        for did in unicode_dids {
            assert!(validate_did(did).is_ok(), 
                "Unicode DID '{}' should be valid", did);
        }
    }

    #[test]
    fn test_empty_string_fields() {
        let mut agent = create_valid_agent();
        agent.did = "".to_string();
        
        let result = validate_agent_data(&agent);
        assert!(matches!(result, Err(ValidationError::InvalidDid(_))));
    }

    #[test]
    fn test_max_u32_values() {
        let mut agent = create_valid_agent();
        agent.total_interactions = u32::MAX;
        agent.total_reviews = u32::MAX;
        // These values will cause the sum to overflow when added
        agent.positive_reviews = u32::MAX / 2 + 1;
        agent.negative_reviews = u32::MAX / 2 + 1;
        agent.average_rating = Some(3.5);
        
        // This will fail because positive + negative != total_reviews
        let result = validate_review_counts(&agent);
        assert!(result.is_err());
        assert!(matches!(result, Err(ValidationError::InconsistentReviews)));
    }

    #[test]
    fn test_validation_performance() {
        use std::time::Instant;
        
        let agent = create_valid_agent();
        let start = Instant::now();
        
        // Run validation 1000 times
        for _ in 0..1000 {
            let _ = validate_agent_data(&agent);
        }
        
        let duration = start.elapsed();
        let avg_time = duration.as_micros() as f64 / 1000.0;
        
        // Should be well under 1ms per validation
        assert!(avg_time < 1000.0, 
            "Validation took {} microseconds on average, should be < 1000", avg_time);
    }
}